CAGA-POSITIVE HELICOBACTER-PYLORI POPULATIONS IN CHINA AND THE NETHERLANDS ARE DISTINCT

The aim of this research was to study whether and to what extent Chine se cagA-positive Helicobacter pylori isolates differ from those in The Netherlands, Analysis of random amplified polymorphic DNA (RAPD)-PCR- assessed DNA fingerprints of chromosomal DNA of 24 cagA-positive H. py lori isolates from Dutch (Iz = 12) and Chinese (n = 10) patients yield ed the absence of clustering. Based on comparison of the sequence of a 243-nucleotide part of cagA, the Dutch (group I) and Chinese (group I I) H. pylori isolates formed two separate branches with high confidenc e limits in the phylogenetic tree, These two clusters were not observe d when the sequence of a 240-bp part of glmM was used in the compariso n. The number of nonsynonymous substitutions was much higher in cagA t han in glmM, indicating positive selection. The average levels of dive rgence of cagA at the nucleotide and protein levels between group I an d II isolates were found to be high, 13.3 and 17.9%, respectively. Pos sibly, the pathogenicity island (PAI) that has been integrated into th e chromosome of the ancestor of H. pylori now circulating in China con tained a different cagA than the PAI that has been Integrated into the chromosome of the ancestor of H. pylori now circulating in The Nether lands. We conclude that in China and The Netherlands, two distinct cag A-positive H. pylori populations are circulating.